1. Technical Field
This invention relates generally to keyless entry systems, and more particularly to a system that activates a vehicle-mounted light and horn by remote control, that indicates vehicle location, and that generates a warning for repulsing a possible aggressor by, for example, locking or unlocking a door or trunk of a vehicle.
2. Discussion
A conventional keyless entry system locks/unlocks a vehicle door at a site distant from the vehicle, by, for example, remotely operating a door-lock actuator. In this system, when a user operates a transmitter operation switch, radio waves are transmitted from the transmitter, and the radio waves are received by a vehicle-mounted receiver. However, the transmission power of the radio waves is uniform. Therefore, it is necessary to transmit the radio waves within a range of the receiver.
However, a user may not be aware of this distance. Also, the above-described receiver range varies according to surrounding circumstances. Because of this, in a case where the transmitter location is outside the receiver's range, the radio waves are not received when the operation switch is operated, and locking or unlocking of the door cannot be executed. Consequently, it is necessary to approach the vehicle up to the receiver range and again operate the transmitter operation switch.
Constantly boosting the transmission power of the radio waves transmitted from the transmitter may also be considered as a method for solving such problems. In this case, the amount of electrical power that is consumed increases with each transmission. However, such a method wastes power, as the transmitter frequently is operated at a location near the receiver within the receivable range of the receiver.
Additionally, it has recently become possible to also include a trunk-open function, a car-finder function, and a panic function in addition to the above lock.backslash.unlock function. A trunk open function allows a user to remotely open a car trunk to facilitate placement/removal of an object into/out of the trunk. A car-finder function enables a user to easily verify the location of his or her vehicle by illuminating a vehicle-mounted light or the like by remote operation in a case where the precise location of his or her vehicle is not known, for example in a situation where many vehicles are parked in a large-scale parking area or at night. A panic function flashes a light or sounds a horn to repulse a potential aggressor or the like, for example in a case where a person is vandalizing the user's vehicle, or a potential aggressor has been discovered near the user's vehicle.
There is a wide range of functions that can be achieved in a keyless entry system in this way, and these are devised so as to be able to be enable at a single transmitter. For example, operation switches of a plurality of types are provided. Even when only a single operation switch is provided, a plurality of functions are discriminated according to an operated state thereof, and a radio signal for a desired function thereof can be generated by the transmitter. These radio waves are received by a vehicle-mounted receiver as was described above. However, because the transmission power of the transmitter is uniform, the distance at which remote operation is possible is the same for any of the above-described plurality of functions, thereby resulting in the following potential problems.
1) Regarding, for example, the above-described trunk-open function, the trunk is usually opened to allow placement of an object in the trunk or to allow removal of an object from the trunk. Therefore, it is sufficient to be able to perform remote operation in the immediate vicinity of the vehicle. However, when operation is possible even at a considerable distance from the vehicle, in a case where the trunk is opened by erroneous operation, the possibility exists that the car may be driven with the trunk still opened. To the contrary, regarding the door-lock/unlock function, even when the door is unlocked due to erroneous operation, the unlocked door is noticed when the user enters the car. Therefore, there is no problem as described above with the trunk.
2) Conversely, in the case of the panic function, it is preferred that operation be possible even at a location distant from the vehicle. This is because panic operation, as was described above, flashes a light or sounds a horn to repulse a potential aggressor, for example in a case where a person is vandalizing the user's vehicle, or when a potential aggressor has been discovered near the user's vehicle. However, when the operating distance thereof is short, the panic function cannot immediately be performed in a case where a potential aggressor has been discovered, and the user must approach to within the operating distance. Because this makes it difficult to adequately enable the panic function, it is preferred that operation be possible even at a location distant from the vehicle. Additionally, it is conceivable that the above-described potential aggressor may retaliate and inflict damage or injury as a result of the panic function having been demonstrated. In order to avoid such a situation, it is preferred that operation be possible from as distant a location as possible.